Experimental investigation to thermal performance of different photo voltaic modules for efficient system design

https://doi.org/10.1016/j.aej.2022.06.037 1110-0168 2022 THE AUTHORS. Published by Elsevier BV on behalf of Faculty of Engineering, Alexandria University This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Saad Ur Rehman , M. Farooq *, Adnan Qamar , M. Usman , Gulzar Ahmad , M. Sultan , M. Wajid Saleem , Ijaz Hussain , M. Imran *, Qasim Ali , M. Yasar Javaid , Farrukh A. Siddiqui h,*


Introduction
Every year a huge amount of revenue is spent to buy crude oil to fulfill energy demand that put a heavy burden on the economy of the any country.Abrupt increase of energy demand and depleting conventional fossil fuels has drawn attention of investors, direct buyer as well as the researcher to shift on renewable energy and start the projects to utilize hydel power, biomass gas, ocean tidal wave, solar power energy and wind energy.This will not only fulfil the current needs of the society but will also minimize the environmental contamination caused by conventional energy sources, i.e. crude oil, natural gas and coal [1][2][3][4][5][6][7][8].In the present era, the energy shortage is the most common and important issue.Due to unbalance in demand and supply, energy deficit has been increasing [9][10][11][12][13][14][15], leading towards the economic shutdown gradually.At the moment the setup electric power production is approximate 23,500 megawatt (MW) and energy shortfall lies in between 3000 MW and 6000 MW in peak hours [16].During summer season energy deficit reaches to its maximum level which leads the country under severe load shedding of several hours, in industrial, metropolitan and remote places [17][18][19][20][21]. Approximate 175,800 Giga watts (GW) power was evaluated over the total area under the 5.3 kWh/m 2 mean daily solar irradiances, which is equivalent to the 19 MJ/m 2 per year that show the strong potential of solar energy in this region consuming only 0.001% of this total solar energy to produce electric power which is equivalent to 16-18 Giga watt (GW) [16].
Renewable energy resources are globally used, however solar energy has its own significance and a fraction of energy coming from sun could solve all energy problems of the country.Solar energy is very fair and clean which causes no pollu-tion.Now it is time to invest in solar power projects that is crucial and is the need of the hour [22][23][24][25][26].
Performance analysis and the variations estimated in the measured data are crucial to know for the prediction of best PV module in any particular weather conditions [27][28][29][30].Different research scholars have evaluated the PV performance in different climates.Conventional energy sources are reducing, and energy demand is still increasing day by day, which created a very serious energy short fall in the country.The country has become distinguished among the other countries across the globe due to the availability of long sunshine hours suitable for photovoltaic implementation for power production.It has the potential to fulfil the energy needs of domestic, rural, industrial and irrigation sectors [31][32][33][34][35][36][37].
The aim of this study is to focus on the outdoor characterization of three commercially available PV modules in a tropical climate and to examine the performance ratio (PR) with of different performance characteristics.Each module was tested with the IV curves of Copper Indium Gallium di Selenide (CIGS) PV modules, c-Si, and p-Si modules by availing the facility of monitoring system under real time outdoor conditions.The data was collected hourly between 9 am to 5 pm for alternative days of all the months of year.The solar irradiance was recorded after every 10 min that represent 28,000 IV curves of data set for 240 points each.To attain this objective, study is established to determine the module efficiency, performance ratio, power output and temperature effect on the performance of commercially available PV modules.This paper also presented PV system designers on the variation of these coefficients in the field and the fill factor with combination of irradiance and temperature.In general perspective, the wafer technologies performs better than the thin film technol- ogy, but on the other hand thin-film technology was found to be degradation [38].Investigation and experimental study were performed in Malaysia region for the interpretation of the efficiency of four certain types of selected solar panels which belonging to copper indium diselenide, poly-crystalline silicon, monocrystalline silicon, crystalline silicon module with laser grooved buried contact, and amorphous silicon (a-Si) in outdoor weather conditions.This study defined that behavior of poly and mono-crystalline performed with high efficiency at high degree of temperature and amorphous silicon produced well results of efficiency in partially sunny and cloudy weather [39].Experimental study was conducted for more than a whole year in the moderate and less harsh temperature climate region of Perth, located in continent of western Australia, Measurements made significant difference among the selected PV modules technology Copper indium diselenide, poly-crystalline silicon, mono-crystalline silicon, crystalline silicon module with laser grooved buried contact, amorphous silicon (a-Si) and measurements result showed that triple junction a-Si generate 14-15% more power in summer season under diffuse sun irradiance and 8 percent in cool winter season than other modules used in this study [40].Experimental study was carried out for the winter season in the climate of Taxila.Performance ratio (ṔR) for selected PV modules (mono-crystalline, polycrystalline and amorphous silicon) was calculated and the results concluded that mono-crystalline module produced 13 percent efficiency (ὴ) in partially sunny and cloudy weather.Amorphous silicon module generates 1.03 mean performance ratio (ṔR) which was significantly more than other modules under the same environment factors where experiment was performed.Furthermore, Module efficiency (ὴ) and performance ratio was declined when temperature of the module gradually increase [41].
Temperature is a cognitive factor that tend to have an effect on the resultant output of PV modules [42][43][44][45][46][47][48].The temperature increases on the surface of panel effects its performance and thermal properties.This paper examines the effect of heat on the parameters linked with PV power, output performance and efficiency.Photovoltaic modules are unique to handle the global energy crisis.High operating temperature effect on each module can be evaluated at real operational outdoor conditions by availing the facility of monitoring system.Efficient PV module cooling technique have to be used for this purpose to improve system performance.The most common processes are heat pipe cooling,forced, hydraulic cooling, thermoelectric cooling, natural air cooling and cooling with PCM heat pipe cooling [49].
Different researchers have observed that intense range of temperatures exert an influence on the results of PV panel system.The study of different researchers describes the methodology, experimental setup and procedure to evaluate the module electrical and thermal parameters at both standard test conditions and outdoor conditions.PV module thermo-grapy examined before the production of PV panels showed that calculated values remain within the manufacturer's purposed values [50][51][52].Experimental study conducted for two years in the tropical region of Japan.Investigation showed that seasonal variation put a vigorous influence on the efficiency of photovoltaic system, by the source of this study amorphous silicon module gave well results of output power (P) and efficiency (ὴ) than polycrystalline silicon in summer [53].Same research study was conducted for whole year in the cool region of Norway.This study monitored the performance of solar panels which had different type of material and easily available in market.It showed that mono-crystalline exhibit much more well performance outcome than poly-crystalline and amorphous silicon modules [54].
The analysis of soil accumulates which change the efficiency of the solar PV module.For this purpose, 70 days' experiments were performed during outdoor condition.The results revealed that the output performance is reduced to 22 percent.After a continuous ten weeks of dust assertion on PV module, mass to volume ratio of dust on the surface from 0.01 g/m 2 at the beginning but it was gradually changed to 6 g/m 2 at the last day of this experimental study [55].The transmission coefficient and energy conservation performance were reduced caused by dust assertion on the exterior upper layer of PV system [41,51,[56][57][58][59][60][61].The rate of reduction in the output efficiency of a crystalline PV system is directly corresponding to quantity of dust assertion on the surface, is equal to 25% per micrometer.It is very crucial to understand that the environmental conditions highly influence the behavior of PV module efficiency [62].Photo degradation is the process in which the efficiency and the performance of amorphous silicon tend to show reduction in photoconductivity of photovoltaic material when it is exposed to light, this is also called light induced degradation (LID) [63].Annealing is another process in which temperature that is greater than 150 is involved to degradation of PV modules silicon modules [64].Different PV module evaluated in the tropical climate region of Indonesia and compared the performance of three certain type of PV modules in a moderate open-air weather.Module performance ratio, efficiency and normalized energy yields examined thoroughly of every module and investigate the thermal and solar irradiances effect.Mono-crystalline showed healthier results of module output efficiency and also good source of power production at moderate outdoor condition.Module efficiency and performance ratio was declined when temperature of the module gradually increase [65].
This research work consists of experimental investigation, evaluation and analyses for the thermal performance of different PV module for efficient system design under varying weather conditions.After every 20 min, approximately 30% solar irradiance reaches the earth which is enough to meet the energy demands of the global community.However, making efficient use of solar energy is not an easy task.This way allowed the maximum capturing of solar irradiance [66].The data was collected hourly from 9 am to 5 pm after every 30 s for alternative days of all the months of year and sometime experiment had to stop due to rainy and stormy weather.In this study solar radiation values calculated through pyranometer for each PV modules.The solar irradiance was recorded after every 30 s. K-type thermocouples were installed at the central cell of each PV module to examine the overall module temperature.All the measured parametric values were recorded through data monitoring system.The data was collected for varying conditions including sunny, partially cloudy and cloudy days.PV modules used in this study expressed different behavior on different climate conditions.To attain this objective, a comparative study is established between module efficiency, performance ratio, power output and temperature effect to calculate the performance of commercially Photovoltaic modules like thin plate Copper indium diselenide, poly-crystalline silicon, mono-crystalline silicon, micro crystalline silicone and amorphous silicon for complete year.

Experimental setup and data collection
Photovoltaic module of five dissimilar materials (thin plate Copper indium diselenide, poly-crystalline silicon, monocrystalline silicon, micro crystalline silicone and amorphous silicon) were analyzed in this study.The experimental setup consists of PV modules, a variable load resister, digital pyranometer, ammeter and voltmeter, data logger for data mongering system and.K-type thermocouples (OEM WRR2-130) to calculate the average temperature of PV modules.A clarified form of experimental setup is shown in Fig. 1.PV modules (Canadian solar system,) were used to capture the solar radiations from natural sun.Ammeter (Fluke 77-IV) having DC current range from 0.001 A to 10 A with direct current accuracy of 1.0% +3 and voltmeter (Fluke 87-V) with voltage range from 0.001 V to 1000 V and accuracy of 0.09% +2.34 were used to compute the photovoltaic current and voltage respectively.A variable load resister (3250 VRL) was used as a series resistance or potentiometer with bearing current up to 5 A. Five thermocouples were installed at the back of five dissimilar material PV modules to take the average temperature.Ambient temperature was also computed through the sixth k-type thermocouple.Solar irradiance values were recorded though a pyranometer (SR30-D1), while the rest of data was executed by the data acquisition system.
The output efficiency of different photovoltaic modules strongly depends on perfect orientation, positioning and tilt angle of photovoltaic modules.The required tilt angle of photovoltaic modules is different for different positions and seasonal conditions.For maximum output power, a large tilt angle is required in winter season and comparative small tilt angle in summer.In the existing literatures many researchers have reported that the tilt angle of a fixed PV module is equal to the latitude angle of that place.If adjustment of PV module is needed twice in a year (summer winter and seasons), then angle of inclination or tilt angle was adjusted according to well-known rule as presented in equation ( 1) and ( 2) [41,51,67].
The latitude of experimental setup location was 31.69°.Using equation (1) and equation (2) tilt angle of 16.69°and 46.69°were observed during summer and winter respectively.It has been seen that tilt angle mostly depends upon the time of year.In the Fig. 2, the PV module is directly perpendicular to the solar irradiance angle (h).Increase in the output power of module is achieved with decrease in the angle (h) and modules have maximum power when i.e. sun is at normal to the face of PV module.E represents the solar irradiance reaching to the module surface.
Experimentation was executed in the outdoor weather conditions.The modules were placed at the roof top at a fixed tilt angle of 16.69°for summer season and 46.69°for winter season with horizontal plane as per latitude of 31.69°[41,51].The characteristic parameters of PV modules were obtained from I to V curve, drawn by using variable resistance and multimeters, the data acquisition system calculated module power output from the module voltage and module current measurements that are made each second.The performance related all parameters are calculated every second by using equations on the site where setup was installed at required tilt angle and then averaged over hourly intervals.

PV modules rated values and parameters analysis
The study of different researchers describes the methodology, experimental setup and procedure to evaluate the module electrical and thermal parameters at both standard test conditions and outdoor conditions.The performance related parameters are calculated using equations ( 3)-( 7) [40,51].
Power Output.
Normalized Power out put.
Module Efficiency.
Performance Ratio.

PR ¼ ðPmax=PmaxðSTCÞÞ=ððI=1000ÞÞ ð7Þ
The typical conditions at which different PV modules are rated on bases of different variables is called standard test conditions that are shown in Table 1.Actually, standard test conditions (STC) express the industry-wide standard values of performance of different PV modules and indicate an irradiance of 1000 W/m 2 and cell temperature of 25 °C at room with an air mass (AM 1. 5).Natural sun is operated under such conditions that it produces natural light source to test thermal performance of different PV modules.Generally, manufacturer of PV panel proposed the standard test conditions (STC) values for different PV modules.The information given in Table 1. at standard test conditions (STC) includes maximum photo-

Solar irradiance measurement analysis
Finest way is to use solar energy with assistance of PV modules, which directly capture and convert solar radiations into the direct current using equation (3) that is resulted to produce power that is solution to fulfill energy demands.As shown in Figs.3a and 3b, the average value of solar irradiance through-out the year were evaluated with the help of pyranometer.The intensity of solar heat decreases with the reduction in solar irradiance.A maximum absorption rate was computed in the month of June (664.59W/m 2 ) was due to more sun shine hours and high solar intensity, December showed (240.94W/m 2 ) lowest solar irradiance value due to fogy and moisture conditions of the weather that decreased the solar absorption intensity as compared with others months.
In Fig. 3c.solar irradiance value for month of Jun was expressed from 9:00 am to 5:00 pm.Highest average irradiances value 834.23 (W/m 2 ) was observed at 1:00 pm and lowest average solar irradiance 360.19 W/m 2 was examined at 5:00 pm.Solar irradiance intensity from morning 9:00 am to 12:00 pm was increased to reach it maximum peak value at  1:00 pm but afterward its valued was reduced (after noon 2:00 pm to 5:00 pm).The greater and lower average value of solar irradiance in June was because of high and low solar intensity during different hours of the days.

Maximum power output analysis
Maximum power output is the major key parameter to compute the thermal performance of photovoltaic modules at different outdoor conditions under natural sun.Usually currentvoltage curve (I-V curve) is used to express the value of maximum power output.Here, in this research study, high power variable resistance is used for calculating maximum power point by using equation ( 4   solar irradiation of all the months of year.All five modules have liner trend in start with the solar irradiance as the solar irradiance increases, maximum power output of all module showed incremental trend but it declined in the evening as solar irradiance decreased.That mean PV modules produced maximum power at the maximum solar irradiance due to the high solar energy absorption and high thermal conductivity.The maximum power output values of (thin plate Copper indium diselenide, poly-crystalline silicon, mono-crystalline silicon, micro crystalline silicone and amorphous silicon) were observed 20.6 W, 80.4 W, 84 W, 19.1 W and 17.8 W correspondingly in overall year.Mono-crystalline silicon has the highest value of maximum power output in month of June relative to other PV modules shown in Fig. 4b.

Module efficiency analysis
The module efficiency is computed through the formula and is the ratio of maximum output power of module to the total incident solar radiation.This total incident is multiply by active area of the module [16,19].
Figs. 5a and 5b represented, module efficiency value of different PV modules (thin plate Copper indium diselenide, polycrystalline silicon, mono-crystalline silicon, micro crystalline silicone and amorphous silicon) for whole year.It is examined that module efficiency of different types of PV modules are directly linked with maximum power output and inversely related with module temperature [43,[68][69][70].
Fig. 5a showed that different type of PV modules has liner decreasing trend in the beginning with the increase in solar irradiance, PV module efficiency showed decrement trend then incremental trend in the evening as soar irradiance decreased.PV module efficiency of (thin plate Copper indium diselenide, poly-crystalline silicon, mono-crystalline silicon, micro crystalline silicone and amorphous silicon) were observed 11.6 %,18.6 %, 20.8 %, 7.7 % and 5.2 % respectively in overall year is shown in Fig. 5b.Mono-crystalline silicon exhibit the highest efficiency as compared to other PV modules due to quality of high solar absorptivity property, high temperature gaining property and higher value of thermal conductivity.

Performance ratio analysis
Performance ratio is used conventionally to.
sexpress the relation between maximum output power of the photovoltaic modules calculated at outdoor condition relative to product of Irradiance and maximum out power of the photovoltaic modules computed at standard test conditions (STC).It can calculate the performance efficiency of any type of module using equation ( 7) that can be proved more helpful to finding [19].
Performance ratio showed decrement trend with the increase of module temperature that can be resulted as degradation of PV module in last [69,[71][72][73], it can be clearly seen in Fig. 6a.It can be seen that performance ratio of thin plate Copper indium diselenide, poly-crystalline silicon, mono-  5b Average values of module efficiencies for different PV modules for whole year.crystalline silicon, micro crystalline silicone and amorphous silicon 1.09, 1.16, 1.21, 1.03, 0.96 respectively in Fig. 6b.Comparing all the PV modules used, mono-crystalline silicon PV module has the maximum performance ratio (PR) at different test conditions.

Module temperature analysis
Fig. 7a expressed the average value of temperature for whole year computed through K-type thermocouple (TC 6 ).A maximum average value of temperature was examined at the month of June because of high solar intensity and more sun shine hours and, December showed lowest value due to fogy and moisture conditions of the weather.Fig. 7b shows the temperature variations of five types of PV modules (thin plate Copper indium diselenide, poly-crystalline silicon, mono-crystalline silicon, micro crystalline silicone and amorphous silicon) under natural sunshine.Comparing value of average temperatures of all the PV modules used in this work, mono-crystalline silicon PV module has the highest average value of temperature among all in the month of June due to highest solar absorption than others PV modules.When it comes to compare with all the photovoltaic modules temperature, ambient temperature is lower than module temperature in whole year.The module temperature reduction is also observed due to sudden decrease of solar irradiance.Furthermore, temperature shows direct proportionality with the solar irradiance [74][75][76].Sometime solar cell exhibited greater temperature value than ambient although the intensity level of solar irradiance was not very much.This is because the more energy produces when solar light converted in the heat by stacking in the surface of solar panel which was made of glenzing material.

Normalized power output analysis
Normalized power output efficiency is the ratio of maximum output power of the photovoltaic modules calculated at outdoor condition to maximum output power of the photovoltaic modules computed at standard test conditions (STC).The normalized output power efficiency was calculated by using formula discussed earlier in equation ( 5) [19].Equation (5) shows the relation of normalized power out, where gp is normalized output power efficiency,Pmax is maximum output power at outdoor condition measured in (W) and Pmax STC ð Þis maximum output power at standard test conditions also measured in Watt.Normalized power output efficiency of different PV modules (thin plate Copper indium diselenide, poly-crystalline silicon, mono-crystalline silicon, micro crystalline silicone and amorphous silicon) were examined 50.27 %,54.03%, 56.2 %, 47.54 % and 44.38 % respectively in overall year is shown in Figs.8a and 8b Monocrystalline silicon exhibit the highest normalized power output efficiency as compared to other PV modules due to quality of high solar absorptivity property, high temperature gaining property and higher value of thermal conductivity.
Performance analysis results data and their varying behavior are very crucial to know for prediction of best PV module in any particular weather conditions [27][28][29][30].Comparison of all parameters of the selected modules can be examined after the optimization in Table 2 over the whole year.These operational results of all systems by analyzing and comparing their performances under the outdoor weather conditions.The results shown help to understand the operation of different PV systems to conclude the best one material under specific outdoor weather condition and also at STC standard test conditions.Normalized power output efficiency of different PV modules (mono-crystalline, polycrystalline, amorphous silicon, thin plate Copper indium diselenide, micro crystalline) were examined 56.2 %, 54.03 %, 44.38 %, 50.27 % and 47.54 % respectively in overall year.But Mono-crystalline silicon PV module proved to be distinguished due to its good solar absorptivity rate.PV module efficiency of (mono-crystalline, polycrystalline, amorphous silicon, thin plate Copper indium diselenide and micro crystalline silicone) were observed 20.8 %, 18.6 %, 5.2 %, 11.6 % and 7.7 % respectively in overall year.

Conclusion
Solar energy capturing by PV modules technology is persuading approach for producing solar power.In this research study, the thermal performance and thermal conversion efficiency of five photovoltaic modules (thin plate Copper indium diselenide, poly-crystalline silicon, mono-crystalline silicon, micro crystalline silicone and amorphous silicon) is examined experimentally under natural sun and outdoor conditions.The contribution of irradiance absorption rate, maximum power output, module efficiency, performance ratio, module temperature and normalized power output efficiency are disclosed in the perspective of thermal performance.Experimental based outcomes described that.All PV modules expressed good solar energy absorption rate, higher module temperature attains, higher module efficiency, higher performance ratio and higher normalized power output efficiency.Average normalized power out of mono-crystalline silicon showed better result 56.2% than other modules.As before mono crystalline calculated 20.8% module efficiency and 1.21 in performance ratio.Mono-crystalline silicon PV module has 5% to 10% higher performance ratio (PR) and power output than others PV modules at different test conditions in this study.Compared the outcome results with the each other in this experiment study, the growing trend and order of PV modules with regard to thermal performance is mono-crystalline, polycrystalline, thin plate Copper indium diselenide, micro crystalline silicone and amorphous silicon.Mono crystalline is famous for its high module efficiency and high absorptivity due to it make from thin wafers of a single silicon crystal with each silicon atom bonded with four neighboring atoms which periodic across the whole crystal.That enhance the capability of better perform in low light condition and having high PR, Mono crystalline is found to be most suitable and should be preferred in renewable energy to make it dominant with solar energy and mitigate energy import bills and the generation of CO 2 in the atmosphere.
This research duly concerns the photo thermal properties of different photovoltaic modules and applications require further research.

Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Fig. 1
Fig. 1 Positioning of PV module on tilt angle.

Fig. 2
Fig. 2 Experimental setup of solar PV system.
Fig. 3a Solar Irradiance average values for twelve months of whole year.

Fig. 4a
Fig. 4a Average maximum output power trend of different PV modules for twelve months.

Fig. 4b
Fig. 4b Average values of maximum power output for different PV modules for whole year.Fig.5a Average module efficiency of different PV modules for whole year.

Fig. 5a
Fig. 4b Average values of maximum power output for different PV modules for whole year.Fig.5a Average module efficiency of different PV modules for whole year.

Fig. 6a
Fig. 6a Average performance values of different PV modules for whole year.

Fig. 6b
Fig. 6b Average values of performance ratio for different PV modules for whole year.

Fig. 7a
Fig.7aAverage ambient temperature of every month for the whole year from 9:00 AM to 5:00 PM.

Fig. 7b
Fig. 7b Average modules temperature and ambient temperature for whole year.

Fig. 8a
Fig. 8a Average normalized output efficiency for whole year.

Fig. 8b
Fig. 8b Average normalized output efficiency value of different PV modules for whole year.

Table 1
Physical dimension and specification of different photovoltaic modules.

Table 2
Comparison after optimization of different PV modules for whole year.